Novel technique to study the wet chemical etching response of multi-crystalline silicon wafers

Abstract

The current work aimed to demonstrate the application of a technique where white light interferometry (WLI) and Laue X-ray crystallography scanner characterisation were combined to study the chemical etching response of diamond cut multi-crystalline Si (mc-Si) wafers. Using this technique, the effect of different texturing additives (isopropyl alcohol, natrium hypochlorite) was evaluated by examining the topography of the mc-Si surfaces before and after etching. The etching responses of monocrystalline Si wafers of (100), (110) and (111) orientations were used as reference for comparison with the multi-crystalline wafers investigated. The texturing results illustrated the influence of different crystal-orientations on the etching rate. It was revealed that for the mc-Si wafers, the etching speed of the different crystal grain-planes is increasing with their crystallographic similarity with the main (hkl) planes (100, 110,111). The comparison of isopropyl alcohol (IPA) and sodium hypochlorite (NaOCl) additives to KOH solutions showed that NaOCl additive is favourable for the polishing of mc-Si wafers, while IPA can be used as polishing only for crystal grains close to the (111) orientation.